SQLite Source Repository

This repository contains the complete source code for the SQLite database
engine. Some test scripts are also include. However, many other test scripts
and most of the documentation are managed separately.

If you are reading this on a Git mirror someplace, you are doing it wrong.
The official repository is better. Go there
now.

Compiling

First create a directory in which to place
the build products. It is recommended, but not required, that the
build directory be separate from the source directory. Cd into the
build directory and then from the build directory run the configure
script found at the root of the source tree. Then run "make".

For example:

tar xzf sqlite.tar.gz ;# Unpack the source tree into "sqlite"
mkdir bld ;# Build will occur in a sibling directory
cd bld ;# Change to the build directory
../sqlite/configure ;# Run the configure script
make ;# Run the makefile.
make sqlite3.c ;# Build the "amalgamation" source file
make test ;# Run some tests (requires Tcl)

See the makefile for additional targets.

The configure script uses autoconf 2.61 and libtool. If the configure
script does not work out for you, there is a generic makefile named
"Makefile.linux-gcc" in the top directory of the source tree that you
can copy and edit to suit your needs. Comments on the generic makefile
show what changes are needed.

Using MSVC

On Windows, all applicable build products can be compiled with MSVC.
First open the command prompt window associated with the desired compiler
version (e.g. "Developer Command Prompt for VS2013"). Next, use NMAKE
with the provided "Makefile.msc" to build one of the supported targets.

There are several build options that can be set via the NMAKE command
line. For example, to build for WinRT, simply add "FOR_WINRT=1" argument
to the "sqlite3.dll" command line above. When debugging into the SQLite
code, adding the "DEBUG=1" argument to one of the above command lines is
recommended.

SQLite does not require Tcl to run, but a Tcl installation
is required by the makefiles (including those for MSVC). SQLite contains
a lot of generated code and Tcl is used to do much of that code generation.
The makefiles also require AWK.

Source Code Tour

Most of the core source files are in the src/ subdirectory. But
src/ also contains files used to build the "testfixture" test harness;
those file all begin with "test". And src/ contains the "shell.c" file
which is the main program for the "sqlite3.exe" command-line shell and
the "tclsqlite.c" file which implements the bindings to SQLite from the
Tcl programming language. (Historical note: SQLite began as a Tcl
extension and only later escaped to the wild as an independent library.)

Test scripts and programs are found in the test/ subdirectory.
There are other test suites for SQLite (see
How SQLite Is Tested)
but those other test suites are
in separate source repositories.

The ext/ subdirectory contains code for extensions. The
Full-text search engine is in ext/fts3. The R-Tree engine is in
ext/rtree. The ext/misc subdirectory contains a number of
smaller, single-file extensions, such as a REGEXP operator.

The tool/ subdirectory contains various scripts and programs used
for building generated source code files or for testing or for generating
accessory programs such as "sqlite3_analyzer(.exe)".

Generated Source Code Files

Several of the C-language source files used by SQLite are generated from
other sources rather than being typed in manually by a programmer. This
section will summarize those automatically-generated files. To create all
of the automatically-generated files, simply run "make target_source".
The "target_source" make target will create a subdirectory "tsrc/" and
fill it with all the source files needed to build SQLite, both
manually-edited files and automatically-generated files.

The SQLite interface is defined by the sqlite3.h header file, which is
generated from src/sqlite.h.in, ./manifest.uuid, and ./VERSION. The
Tcl script at tool/mksqlite3h.tcl does the conversion.
The manifest.uuid file contains the SHA1 hash of the particular check-in
and is used to generate the SQLITE_SOURCE_ID macro. The VERSION file
contains the current SQLite version number. The sqlite3.h header is really
just a copy of src/sqlite.h.in with the source-id and version number inserted
at just the right spots. Note that comment text in the sqlite3.h file is
used to generate much of the SQLite API documentation. The Tcl scripts
used to generate that documentation are in a separate source repository.

The SQL language parser is parse.c which is generate from a grammar in
the src/parse.y file. The conversion of "parse.y" into "parse.c" is done
by the lemon LALR(1) parser generator. The source code
for lemon is at tool/lemon.c. Lemon uses a
template for generating its parser. A generic template is in tool/lempar.c,
but SQLite uses a slightly modified template found in src/lempar.c.

Lemon also generates the parse.h header file, at the same time it
generates parse.c. But the parse.h header file is
modified further (to add additional symbols) using the ./addopcodes.awk
AWK script.

The opcodes.h header file contains macros that define the numbers
corresponding to opcodes in the "VDBE" virtual machine. The opcodes.h
file is generated by the scanning the src/vdbe.c source file. The
AWK script at ./mkopcodeh.awk does this scan and generates opcodes.h.
A second AWK script, ./mkopcodec.awk, then scans opcodes.h to generate
the opcodes.c source file, which contains a reverse mapping from
opcode-number to opcode-name that is used for EXPLAIN output.

The keywordhash.h header file contains the definition of a hash table
that maps SQL language keywords (ex: "CREATE", "SELECT", "INDEX", etc.) into
the numeric codes used by the parse.c parser. The keywordhash.h file is
generated by a C-language program at tool mkkeywordhash.c.

The Amalgamation

All of the individual C source code and header files (both manually-edited
and automatically-generated) can be combined into a single big source file
sqlite3.c called "the amalgamation". The amalgamation is the recommended
way of using SQLite in a larger application. Combining all individual
source code files into a single big source code file allows the C compiler
to perform more cross-procedure analysis and generate better code. SQLite
runs about 5% faster when compiled from the amalgamation versus when compiled
from individual source files.

The amalgamation is generated from the tool/mksqlite3c.tcl Tcl script.
First, all of the individual source files must be gathered into the tsrc/
subdirectory (using the equivalent of "make target_source") then the
tool/mksqlite3c.tcl script is run to copy them all together in just the
right order while resolving internal "#include" references.

The amalgamation source file is more than 100K lines long. Some symbolic
debuggers (most notably MSVC) are unable to deal with files longer than 64K
lines. To work around this, a separate Tcl script, tool/split-sqlite3c.tcl,
can be run on the amalgamation to break it up into a single small C file
called sqlite3-all.c that does #include on about five other files
named sqlite3-1.c, sqlite3-2.c, ..., sqlite3-5.c. In this way,
all of the source code is contained within a single translation unit so
that the compiler can do extra cross-procedure optimization, but no
individual source file exceeds 32K lines in length.

Unfortunately, years of effort have gone into optimizating SQLite, both
for small size and high performance. And optimizations tend to result in
complex code. So there is a lot of complexity in the SQLite implementation.

Key files:

sqlite.h.in - This file defines the public interface to the SQLite
library. Readers will need to be familiar with this interface before
trying to understand how the library works internally.

sqliteInt.h - this header file defines many of the data objects
used internally by SQLite.

parse.y - This file describes the LALR(1) grammer that SQLite uses
to parse SQL statements, and the actions that are taken at each step
in the parsing process.

vdbe.c - This file implements the virtual machine that runs
prepared statements. There are various helper files whose names
begin with "vdbe". The VDBE has access to the vdbeInt.h header file
which defines internal data objects. The rest of SQLite interacts
with the VDBE through an interface defined by vdbe.h.

where.c - This file analyzes the WHERE clause and generates
virtual machine code to run queries efficiently. This file is
sometimes called the "query optimizer". It has its own private
header file, whereInt.h, that defines data objects used internally.

btree.c - This file contains the implementation of the B-Tree
storage engine used by SQLite.

pager.c - This file contains the "pager" implementation, the
module that implements transactions.

os_unix.c and os_win.c - These two files implement the interface
between SQLite and the underlying operating system using the run-time
pluggable VFS interface.

shell.c - This file is not part of the core SQLite library. This
is the file that, when linked against sqlite3.a, generates the
"sqlite3.exe" command-line shell.

tclsqlite.c - This file implements the Tcl bindings for SQLite. It
is not part of the core SQLite library. But as most of the tests in this
repository are written in Tcl, the Tcl language bindings are important.

There are many other source files. Each has a suscinct header comment that
describes its purpose and role within the larger system.